Isamu Takeshita (竹下 勇, Takeshita Isamu; 5 January 1870 – 1 July 1949) was an admiral in the Imperial Japanese Navy. He was also a diplomat whose accomplishments included helping end the Russo-Japanese War favorably for Japan and obtaining former German possessions in the Pacific for Japan following World War I. In addition, he was a patron and practitioner of the Japanese martial arts, especially judo, sumo, and aikido.

Born Yamamoto Jiro into a samurai class family in Kagoshima, Satsuma domain (present-day Kagoshima prefecture), he was adopted into the Takeshita family as a boy.

Takeshita entered the 15th class of the Imperial Japanese Naval Academy in 1892, and he graduated third in a class of eighty students. He entered naval service as a midshipman in 1889; his first ship was the armored corvette Kongo. In 1898, he attended the Japanese Naval War College, which had been founded that same year.

Because he was fluent in English, Takeshita was posted overseas at various times as a naval attaché. In October 1902, he was appointed Japan's naval attaché to the United States. In this role, Takeshita was an active participant in negotiations mediated by President Theodore Roosevelt that led to the Treaty of Portsmouth, ending the Russo-Japanese War. During 1904, he also helped Roosevelt obtain the services of judo teacher Yamashita Yoshitsugu, first for Roosevelt himself and then for the United States Naval Academy. Takeshita's commands included the cruisers Suma, Kasuga, Izumo, Tsukuba and the battleship Shikishima.

Takeshita was a member of the Japanese diplomatic mission to the United States in 1917, the Paris Peace Conference of 1919, and the League of Nations. In these positions, he played a leading role in Japan's obtaining former German holdings in the Central and Western Pacific. For these efforts, he was awarded the Order of the Rising Sun (1st class). Takeshita returned to Japan to accept a posting as commander-in-chief of the Combined Fleet on 1 December 1922, a position he held until January 1924. His subsequent billets included Commander of the Kure Naval District. He was placed on the retired list in November 1929.

During late summer 1935, Takeshita made his fifth trip to the United States. His mission was to try to explain to American audiences that Japan's invasion of China in the Second Sino-Japanese War, was to stop the spread of Communism. As for Japan's relationship with the United States, Takeshita stated that "No Japanese warship has ever crossed the Pacific except on a mission of peace," he said during a radio broadcast in San Francisco. "No Japanese soldier has ever come to these shores except on a similar mission."

In February 1937, Takeshita was appointed head of the Japanese Boy Scouts, Sea Scouts, and YMCA. This was part of the general militarization of Japanese sports and athletics taking place at that time. Later that year, he was also approached about becoming the head of the Japanese Amateur Athletic Federation, but he declined this offer.

In May 1939, Takeshita became the third president of the Japan Sumo Association. He held this post until November 1945.